This project tests the hypothesis that the functional integration of the autonomic system is variably altered during exposure to inhalation anesthetics in a dose dependent manner. Animals, chronically instrumented both for multiple afferent stimulation and for cardiovascular monitoring, will be studied at each of five different steady state alveolar concentrations of each agent, each animal serving as its own control. At each anesthetic concentration, 7 different cardiovascular parameters will be examined for their response to graded stimulation of each of 6 different modalities. This information will provide a qualitative and quantitative estimate of what circulatory reflexes are accentuated, depressed, or reversed at each specific drug concentration. If, at a certain concentration, all responses are found to be minimized, this clinically important zone will be used as an endpoint to define and compare autonomic equipotent concentrations.